Optical device fabrication

ABSTRACT

Transparent conductive coatings are polished using particle slurries in combination with mechanical shearing force, such as a polishing pad. Substrates having transparent conductive coatings that are too rough and/or have too much haze, such that the substrate would not produce a suitable optical device, are polished using methods described herein. The substrate may be tempered prior to, or after, polishing. The polished substrates have low haze and sufficient smoothness to make high-quality optical devices.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/347,227, filed Mar. 25, 2014, entitled “Optical Device Fabrication”,which is a national stage application under 35 U.S.C. § 371 toInternational Application Number PCT/US2012/057606 (designating theUnited States), filed on Sep. 27, 2012 and entitled “Optical DeviceFabrication”, which claims benefit of U.S. Provisional Application No.61/541,999, filed on Sep. 30, 2011, and entitled “Optical DeviceFabrication”, the disclosures of which are hereby incorporated byreference in their entirety and for all purposes.

FIELD

The disclosure relates to smoothing the topology of transparentconductive oxide coatings. More specifically, roughness is mitigated inorder to create more uniform coatings upon which to fabricate opticaldevices.

BACKGROUND

Optical device technology, e.g. electrochromic device technology, hasadvanced to the point where such devices can be fabricated usingindividual layers of materials that make up a “device stack” that isvery thin, e.g., on the order of a few microns or even less than amicron in thickness. With such devices being very thin, uniformity ofthe substrate onto which they are fabricated is important, because theindividual layers of the device stack may be on the order of tens orhundreds of nanometers thick. Non-uniformity in the substrate surfacecan translate into areas of the device stack that do not functionproperly or exhibit electrical shorting or other defectivity.Defectivity in the device stacks can often be correlated to the surfaceroughness of the substrate onto which the device stack is fabricated.

With small-scale production, e.g. in a research and development phase, asubstrate can be carefully selected or fabricated for very highuniformity so that the above-described issues do not arise. Aselectrochromic device fabrication moves to large-scale production, it ismore practical to purchase large area substrates, e.g. float glasscoated with a transparent conducting film, from commercial sources thatproduce such substrates in large volume. The problem that often arisesin such substrates is surface roughness of the pre-formed coatingsthereon. For example, float (soda lime) glass is commercially offeredwith a bilayer coating on one surface. The bilayer includes a firstlayer which is a sodium diffusion barrier to prevent sodium ions fromthe glass from passing through it, and a second layer on the first layerwhich is a transparent conducting layer, e.g., a doped tin oxide such asindium tin oxide, fluorinated tin oxide, or similar transparentconducting coating. These coated glasses are well suited for a number ofapplications, including production of optical coatings thereon; however,for functioning device stacks on the order of a few microns or less inthickness, the surface roughness of these pre-formed coatings may beproblematic at least for the reasons articulated above.

Also, there is an inverse relation between the desired properties of aglass substrate for optical coatings and some of the actual propertiesof the glass substrate when one moves to large scale production. Forexample, it is desirable to have a transparent conducting coating (e.g.,film) with low sheet resistance across a glass substrate with anelectrochromic device fabricated thereon. The lower the sheetresistance, the faster the electrochromic device may be able to switch.However, when moving to large scale substrate production, in order toproduce highly reliable coatings, transparent conductors are generallymade with larger grain size. Oftentimes these transparent coatings willhave a low sheet resistance, but will also have a higher haze (lightscattering) due to the larger grain size of the coatings. This haze isnot a desired property of some final optical device products, e.g.,electrochromic windows having electrochromic devices. For such windows,clarity and high contrast are important qualities. The larger grain sizealso contributes to the surface roughness, which is undesirable for thereasons described above. For context, transparent conductor coatings inlarge scale production substrates may have a surface roughness (Ra) ofabout 7 nm to 10 nm, and sometimes higher than 10 nm. For conventionalapplications, these surface roughness and haze properties may beconsidered well within acceptable levels or desired levels. For example,some optical device applications, such as photovoltaic cells, benefitfrom higher haze and roughness levels due to the increased scattering ofincident light improving absorption efficiency. There may not be a needto polish a transparent conducting layer for these conventionalapplications.

There have been studies on polishing transparent conducting layers onglass. For example, indium tin oxide (ITO) layers have been polishedusing magnetorheological finishing (MRF) which resulted in a surfacewith surface roughness down to a few nanometers (see e.g.,www.optics.rochester.edu/workgroups/cml/opt307/spr07/chunlin/, lastvisited Sep. 30, 2011). Also, the surface roughness of ITO layers hasbeen reduced using KrF excimer lasers (see J. Vac. Sci. Technol. A 23,1305 (2005). However, these techniques are highly specialized andprohibitively expensive to implement on large area substrates and/or ina mass production setting. One reported method of reducing haze in tinoxide coatings describes, rather than polishing the roughness down,filling in the valleys to smooth the overall contour of the coating (seeU.S. Pat. No. 6,268,059). Compositions and methods that use acidiczirconia or colloidal silica for chemical mechanical polishing of ITOhave also been reported (see US 2007/0190789). Despite these advances,there is a continuing need for new and improved methods of reducing hazeand smoothing the surface of transparent conductive coatings.

SUMMARY

Transparent conductive coatings are polished using particle slurries incombination with mechanical shearing force, such as can be provided by apolishing pad. Substrates having transparent conductive coatings thatare too rough and/or have too much haze, such that the substrate wouldnot produce a suitable optical device, are polished using methodsdescribed herein. The substrates may be tempered prior to, or after,polish. The polished substrates have low haze and sufficient smoothnessto make high-quality optical devices.

Abrasive particles of between about 0.1 μM and about 1 μM averagediameter can be used. In certain embodiments, particles of 0.25 μM orlarger average diameter are used. In one embodiment alumina particleslurries are used. In a particular embodiment, alumina slurries withparticles of average diameter of between about 0.25 μM and about 1 μMare used. These and other aspects are described in more detail below. Inone embodiment, alumina slurries with particles of average diameter ofabout 1 μM are used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process flow outlining aspects of methods described herein.

FIG. 2 is a process flow outlining aspects of a method of forming an allsolid state and inorganic electrochromic device.

FIG. 3 is a schematic rendering of an electrochromic device on asubstrate.

FIG. 4 includes transmission electron microscope images (TEMs) of atransparent conductor layer with polishing using methods as describedherein as compared to a transparent conducting layer without polish.

DETAILED DESCRIPTION

The inventors have found that for electrochromic devices having anoverall thickness in the range of a few microns or less, whereindividual layers of the device stack are on the order of 600 nm orless, and sometimes as thin as tens of nanometers, the surface roughnessmay be too high and the haze of the final product (e.g., electrochromicwindow) may be unacceptable given the high clarity and contrast demandedby the market. The surface roughness, if too high, of a transparentconducting layer can adversely affect the functionality of an opticaldevice, e.g. an electrochromic device, fabricated thereon. Also, themarket demands optical devices and their final products have very lowhaze. For example, electrochromic windows are oftentimes deemedunacceptable if their level of haze is above 1%.

Methods described herein mitigate surface roughness and/or haze of asubstrate prior to device fabrication thereon. These methods areparticularly applicable for use on transparent conducting layers onglass substrates. Even more particularly, the methods are useful tomitigate roughness and/or haze on transparent conductive coatings thatare produced via pyrolytic methods, i.e., where the roughness and hazeof the coatings produced by such methods may be acceptable for otheruses, but not so for optical device fabrication. Methods describedherein allow the use of such “crude” coatings in the production ofhighly-specialized device coatings, such as electrochromic coatings forelectrochromic windows. Using methods described herein, the surfaceroughness and haze of such transparent conductive coatings are reducedsignificantly.

In an attempt to reduce haze, the inventors conceived of methodsdescribed herein, and were quite surprised to find that optical devicefunctionality was also dramatically improved. That is, it was known that“spikes” in the topography of transparent conductors can causeelectrical shorts by crossing the layers of an electronic devicefabricated on the transparent conducting layer. However, it was notknown that lesser roughness would improve the functionality of anoptical device to such a degree as has been found with methods describedherein. In fact, roughness in the transparent conducting layer of someprevious optical devices (e.g., photovoltaic cells) had been describedas actually being beneficial (See International Publication No. WO2012/056240). In contrast, it was found that the methods describedherein reduced roughness and also improved the functionality ofelectrochromic devices. For example, all solid state and inorganicelectrochromic devices have a higher resistance to moisture incursion(reduced hermiticity) when fabricated on substrates polished usingmethods described herein, versus substrates without such treatment.Without wishing to be bound by theory, it is believed that by startingwith a smoother substrate, there is less “memory effect” in that thesolid state materials deposited on the polished substrates do not mimic,or are not adversely affected by, what would otherwise be a very roughtopography. For example, crystalline materials may develop or form withfissures or crystal dislocations that can allow moisture incursion intothe lattice.

Mitigation of surface roughness can be performed on a transparentconducting layer of a glass substrate prior to, or after, a temperingprocess. Advantages of these methods may include smoothing the surfaceof the transparent conducting layer, thereby decreasing defectivity inthe electrochromic device fabricated thereon, and also decreasing hazein the final transparent substrate. Other advantages may includenormalization of the surface of the transparent conducting layer,thereby decreasing the amount and variation in contaminants on thesurface (e.g., interleave compounds, organic residues, particles and thelike which are on the glass as purchased). When the methods describedherein are performed prior to, or without, tempering, advantages mayinclude normalizing the glass surface prior to cutting to size,therefore increasing yield, whether or not the glass is eventuallytempered (e.g., the glass may not be tempered but instead laminated tostrengthen the glass). When the methods described herein are performedafter tempering, advantages may include normalizing any surfaceroughness or irregularities that may have arisen as a result of thetempering process that would otherwise detrimentally affect the devicestack performance. That is, glass tempering uses very high temperatures,and the morphology of coatings on the glass may change during thetempering process. Polishing the glass after tempering mitigates changesin topology due to morphology shift as a result of the temperingprocess.

One embodiment is a method of fabricating an electrochromic device on aglass substrate having a transparent conducting layer thereon, themethod including polishing the surface of the transparent conductinglayer to reduce the surface roughness and then fabricating theelectrochromic device thereon. In one embodiment, the glass substrate istempered prior to fabrication of the electrochromic device thereon. Inanother embodiment, the surface of the transparent conducting layer ispolished without first tempering the glass substrate. In one embodiment,the surface of the transparent conducting layer is polished as describedherein and then the glass substrate is tempered. Another embodiment isan electrochromic device fabricated on a glass substrate having apolished transparent conductive layer thereon. In one embodiment, theglass substrate is coated with a tin oxide based transparent conductivelayer. In one embodiment, the tin oxide based transparent conductivelayer is ITO (indium tin oxide) or TEC (fluorinated tin oxide). In aspecific embodiment, the tin oxide based transparent conductive layer isTEC that has been applied to the glass substrate via a pyrolytic method;that is, a precursor material is sprayed or otherwise applied as asolution to the glass substrate and then high heat is used to burn awaycomponents of the precursor material to leave a TEC coating on the glasssubstrate.

Polishing the surface of a transparent conducting layer may be donemechanically using an abrasive preparation, e.g., alumina, ceria, andthe like. Commercially available polishing abrasives, e.g., slurriedabrasive preparations having average particle sizes of between about 0.1μm and about 10 μm, may be used. In certain embodiments, particles withaverage diameters at the larger end of the aforementioned spectrum areused. In one embodiment, particles with an average diameter of betweenabout 0.25 μm and about 10 μm are used. In certain embodiments, alumina(aluminum oxide) particles are used as the abrasive component.

Alumina, as measured on Mohs hardness scale, has a value of 9 (diamondbeing 10). Thus, alumina is harder than other common polishing agentssuch as, ceria (6 on Mohs scale), zirconia (8 on Mohs scale) or silica(8 on Mohs scale). Without wishing to be bound by any particular theory,it is believed that alumina may offer superior polishing of transparentconductors, because of the significant difference in hardness of aluminaas compared to transparent conductors, such as tin oxide based materials(e.g. tin oxide has a Mohs value of 6.5). At the same time, alumina isrelatively inexpensive as compared to, e.g., corundum (9 on Mohs scale)or diamond. In one embodiment, alumina particles having an averageparticle diameter of about 0.25 μm are used in a slurry preparation tomechanically polish the transparent conducting layer. In anotherembodiment, alumina particles having an average particle diameter ofabout 0.5 μm are used in a slurry preparation to mechanically polish thetransparent conducting layer. In yet another embodiment, aluminaparticles having an average particle diameter of about 1 μm are used ina slurry preparation to mechanically polish the transparent conductinglayer.

Since reflective measurements are less useful with transparent layers,the time and amount of polishing can be determined, e.g., by measuringthe sheet resistance of the transparent conducting layer and ceasingpolishing while the sheet resistance remains at an acceptable level.That is, as the polishing operation is carried out, the sheet resistanceof the transparent conducting layer will increase due to the thinning ofthe layer due to removal by polishing. The polishing operation may bestopped before the sheet resistance of the transparent conducting layerincreases to an unacceptable level. For example, the polishing operationmay cease when the measured sheet resistance of the glass substrate isat or near (i.e. slightly above or below) an acceptable level (i.e.maximum acceptable sheet resistance). Sheet resistance may be measured,e.g., periodically measured, during the polishing operation. In thisexample, the time and amount of polishing is based on the measurement ofthe sheet resistance at or near the acceptable level. In one embodiment,the polishing is performed for about 10 minutes to about 3 hours, inanother embodiment about 30 minutes to about 2 hours, and in anotherembodiment for about 1.5 hours.

It has been found that by polishing the transparent conducting layerprior to fabrication of an electrochromic device thereon, defectivity inthe electrochromic device is reduced. This result is not only due toreduction of “spikes” in the transparent conductive layer that can causeshorting shunts through the layers of the electrochromic device, butalso the surface roughness can affect adhesion of the layers depositedthereon. Also, there is the aforementioned “memory effect” when therough topology of the transparent conducting layer is transferred to thelayers of the electrochromic device. That is, the rough topology mayorient crystalline layers atop the transparent conductor and adverselyaffect ionic and/or electrical conduction.

Further, it has been found that substrates with transparent conductinglayers that have larger grain size, which are rougher but have lowersheet resistance, can be used; the transparent conducting layer's sheetresistance increases with polishing, but the low sheet resistanceassociated with a larger grain size transparent conducting layer mayoffset this increase in sheet resistance due to polishing. Thus whatpreviously may have been thought of as an unsuitable substrate uponwhich to fabricate an electrochromic device is converted into a highlysuitable substrate using methods described herein.

Polishing according to methods described herein can achieve typicalsurface roughness on the order of a few nanometers Ra, without having torely on, e.g., magnetorheological finishing (MRF) or high energy lasertreatment. In one embodiment, the transparent coating's roughness ispolished to an Ra of between about 1 nm and about 10 nm, in anotherembodiment between about 1 nm and about 5 nm, in another embodimentbetween about 2 nm and about 3 nm.

After polishing, the transparent substrate is cleaned to remove anyabrasives remaining. The transparent substrate is then ready forfabrication of the electrochromic device thereon, e.g., by sequentiallydepositing an electrochromic device using a single integrated depositionsystem having a controlled ambient environment in which the pressureand/or gas composition are controlled independently of an externalenvironment outside of the integrated deposition system, and thesubstrate does not leave the integrated deposition system at any timeduring the sequential deposition device stack.

Exemplary solid state electrochromic devices, methods, and apparatus formaking them and methods of making electrochromic windows with suchdevices are described in U.S. Non-provisional patent application Ser.No. 12/645,111, entitled “Fabrication of Low Defectivity ElectrochromicDevices,” by Kozlowski et al., U.S. Non-provisional patent applicationSer. No. 12/645,159, entitled “Electrochromic Devices,” by Wang et al.,and U.S. application Ser. No. 12/772,055, filed Apr. 30, 2010, entitled“Electrochromic Devices”, each of which is incorporated by referenceherein for all purposes. One embodiment of fabricating an electrochromicdevice in accord with methods described herein is presented below.

FIG. 1 is a process flow, 100, in accord with methods disclosed herein.Specifically, after a transparent substrate having a transparentconducting layer thereon is received, the transparent conducting layeris polished mechanically, see 105. If the transparent substrate is, e.g.float glass, it may be tempered prior to, or post, polishing. Polishingcan be done by hand or by automated polishing apparatus that is, e.g.,computer controlled to polish to the desired surface roughness and/orsheet resistance level of the transparent conducting layer. In oneembodiment, the sheet resistance of the transparent conducting layer ismeasured periodically during the polishing operation in order to guidethe polishing level. After the transparent conducting layer is polished,the transparent substrate is cleaned to remove abrasive particles andany contaminants, see 110. Cleaning may include using detergents,surfactants, and the like, well known to skilled artisans. Aftercleaning, an electrochromic device is fabricated on the transparentconducting layer, see 115, and the method is complete. Below isdescribed a specific fabrication method of depositing an electrochromicdevice on a transparent conducting layer, which has been polished andcleaned as described herein.

FIG. 2 is a process flow, 200, for depositing an electrochromic (EC)layer (see 205), then a counter electrode (CE) layer (see 215) andultimately forming an interfacial region, functioning as an ionconducting (IC) layer there between. In the described embodiment, the EClayer includes WO₃ with various amounts of oxygen, in particularcompositions and configurations; the CE layer includes NiWO; theinterfacial region includes Li₂WO₄, and, the transparent conductingoxide (TCO) layer includes transparent conducting oxide (TCO) materialssuch as indium tin oxide and fluorinated tin oxide. Different materialscan be used in one or more of the layers of the electrochromic device ofother embodiments.

It should be noted that the layers of the electrochromic devices aredescribed below in terms of solid state materials. Solid state materialsare desirable because of reliability, consistent characteristics andprocess parameters, and device performance. In particular embodiments,the electrochromic devices disclosed herein are entirely solid state andmade in apparatus that allow deposition of one or more layers of thestack in a controlled ambient environment. That is, in apparatus wherethe layers are deposited without leaving the apparatus and without, forexample, breaking vacuum between deposition steps, thereby reducingcontaminants and ultimately improving device performance. In aparticular embodiment, apparatus described herein do not require aseparate target for depositing an IC layer, as is required inconventional apparatus. As one of ordinary skill in the art wouldappreciate, the embodiments disclosed herein are not limited to thesematerials and methods; however, in certain embodiments, all of thematerials making up electrochromic stack are both inorganic and solid.

Referring again to FIG. 2, first an EC layer of WO₃ is deposited, see205. FIG. 3 is a schematic cross-section depicting formation of anelectrochromic device in accord with process flow 200. Specifically,FIG. 3 is used to show a non-limiting example of how an EC layerincluding WO₃ can be formed as part of a stack, where an interfacialregion serving as an IC layer is formed after or while the other layersof the stack are deposited.

Referring to FIG. 3, a layered structure, 300, is depicted. The layeredstructure includes a substrate, 302, which is, for example, glass.Suitable glasses include either clear or tinted soda lime glass,including soda lime float glass. The glass may be tempered or not.Examples of commercially available glass substrates that have atransparent conductive layer coating include conductive layer coatedglasses sold under the trademark TEC Glass™ by Pilkington of Toledo,Ohio, and SUNGATE™ 300 and SUNGATE™ 500 by PPG Industries of Pittsburgh,Pa. TEC Glass™ is a glass coated with a pyrolytically appliedfluorinated tin oxide conductive layer (TEC layer). This TEC layer is anexemplary transparent conductive layer that may be polished according tomethods described herein. The TEC layer is very hard and resistant topolishing, therefore alumina has been found to be a particularly usefulabrasive in polishing TEC layers, since alumina is much harder than TEC.Layer 303 is a sodium diffusion barrier and layer 304 is the polishedtransparent conductive layer.

In some embodiments, the optical transmittance (i.e., the ratio oftransmitted radiation or spectrum to incident radiation or spectrum) ofsubstrate 302 may be, for example, about 90 to 95%, or about 90 to 92%.The substrate may be of any thickness, as long as it has suitablemechanical properties to support the electrochromic device. Whilesubstrate 302 may be of any size, in some embodiments, it is about 0.01mm to about 10 mm thick, or about 3 mm to about 9 mm thick. In oneembodiment, where the substrate is to be incorporated into an insulatedglass unit, and the substrate is 20 inches by 20 inches or larger, e.g.up to 72 inches by 120 inches, 6 mm glass is often used, as itrepresents a good balance between strength and weight considerations(e.g. 9 mm glass is 50% heavier than 6 mm glass, while not providingsignificant strength advantage over 6 mm glass).

In some embodiments, the substrate is architectural glass. Architecturalglass is glass that is used as a building material. Architectural glassis typically used in commercial buildings, but may also be used inresidential buildings, and typically, though not necessarily, separatesan indoor environment from an outdoor environment. In certainembodiments, architectural glass is at least about 20 inches by 20inches, and can be much larger, for example, as large as about 72 inchesby 120 inches. Architectural glass is typically at least about 2 mmthick. Architectural glass that is less than about 3.2 mm thick cannotbe tempered. In some embodiments with architectural glass as thesubstrate, the substrate may still be tempered even after theelectrochromic stack has been fabricated on the substrate. In someembodiments with architectural glass as the substrate, the substrate isa soda lime glass from a tin float lime. The percent transmission overthe visible spectrum of an architectural glass substrate (i.e., theintegrated transmission across the visible spectrum) is generallygreater than about 80% for neutral substrates, but it could be lower forcolored substrates. The percent transmission of the substrate over thevisible spectrum may be at least about 90% (for example, about 90 to92%). The visible spectrum is the spectrum that a typical human eye willrespond to, generally about 380 nm (purple) to about 780 nm (red). Inone embodiment, the transparent conducting layer 304 has a surfaceroughness of about 1 nm to about 5 nm, in another embodiment, about 2 nmto about 3 nm. For the purposes of further description, “substrate 302”refers collectively to layers 302, 303 and 304.

Transparent conductive layers described herein (e.g., layers 304 and312), include transparent conductive oxides (TCOs) materials includingmetal oxides and metal oxides doped with one or more metals. Examples ofsuch metal oxides and doped metal oxides include indium oxide, indiumtin oxide, doped indium oxide, tin oxide, doped tin oxide, zinc oxide,aluminum zinc oxide, doped zinc oxide, ruthenium oxide, doped rutheniumoxide, and the like. In one embodiment, the transparent conductive layer304 with TCO materials is about 20 nm to about 1200 nm thick, in anotherembodiment, about 100 nm to about 600 nm thick, in another embodimentabout 350 nm thick. The transparent conductive layers with TCO materials(i.e., 304 and 312) have an appropriate sheet resistance (R_(s)) due tothe relatively large area spanned by the layers. In some embodiments,the sheet resistance of one or more of the transparent conductive layers304 and 312 is about 5 to about 30 Ohms per square. In some embodiments,the sheet resistance of one or more of the transparent conductive layers304 and 312 is about 15 Ohms per square. It may be desirable that thesheet resistance of each of the two transparent conductive layers (i.e.,304 and 312) to be about the same in some cases. In one embodiment, thetwo transparent conductive layers, for example layers 304 and 312, eachhave a sheet resistance of about 10 to 15 Ohms per square. In oneembodiment, the transparent conductive layer (e.g., 304 or 312) may bepolished using methods described herein while the measured sheetresistance of the transparent conductive layer remains at or below anacceptable level (e.g., levels in the range of 5 to about 30 Ohms persquare). Some examples of acceptable levels include 5, 10, 15, 20, 25,and 30 Ohms per square.

Consistent with process flow 200 of FIG. 2, the device stack 320 of FIG.3 includes an electrochromic layer, 306, deposited on top of a first(polished) transparent conductive 304 (i.e. transparent conductive layerhaving TCO materials). The electrochromic layer (e.g., 306) may containany one or more of a number of different electrochromic materials,including metal oxides. Such metal oxides include, for example, tungstenoxide (WO₃), molybdenum oxide (MoO₃), niobium oxide (Nb₂O₅), titaniumoxide (TiO₂), copper oxide (CuO), iridium oxide (Ir₂O₃), chromium oxide(Cr₂O₃), manganese oxide (Mn₂O₃), vanadium oxide (V₂O₅), nickel oxide(Ni₂O₃), cobalt oxide (Co₂O₃) and the like. In some embodiments, themetal oxide is doped with one or more dopants such as, for example,lithium, sodium, potassium, molybdenum, niobium, vanadium, titanium,and/or other suitable metals or compounds containing metals. Mixedoxides (for example, W—Mo oxide, W—V oxide) are also used in certainembodiments, that is, the electrochromic layer may include two or moreof the aforementioned metal oxides. An electrochromic layer (e.g., 306)including a metal oxide is capable of receiving ions transferred from acounter electrode layer (e.g., layer 310).

In some embodiments, tungsten oxide or doped tungsten oxide is used forthe electrochromic layer (e.g., layer 306). In one embodiment, theelectrochromic layer is made substantially of WO_(x), where “x” refersto an atomic ratio of oxygen to tungsten in the electrochromic layer,and x is about 2.7 to 3.5. It has been suggested that onlysub-stoichiometric tungsten oxide exhibits electrochromism; i.e., thatstoichiometric tungsten oxide, WO₃, does not exhibit electrochromism. Ina more specific embodiment, WO_(x), where x is less than 3.0 and atleast about 2.7 is used for the electrochromic layer. In anotherembodiment, the electrochromic layer is WOx, where x is about 2.7 toabout 2.9. Techniques such as Rutherford Backscattering Spectroscopy(RBS) can identify the total number of oxygen atoms which include thosebonded to tungsten and those not bonded to tungsten. In some instances,tungsten oxide layers where x is 3 or greater exhibit electrochromism,presumably due to unbound excess oxygen along with sub-stoichiometrictungsten oxide. In another embodiment, the tungsten oxide layer hasstoichiometric or greater oxygen, where x is about 3.0 to about 3.5. Insome embodiments, at least a portion of the EC layer has an excess ofoxygen. This more highly oxygenated region of the EC layer is used as aprecursor to formation of an ion conducting electron insulating regionwhich serves as an IC layer. In other embodiments, a distinct layer ofhighly oxygenated EC material is formed between the EC layer and the CElayer for ultimate conversion, at least in part, to an ion conductingelectronically-insulating interfacial region.

In certain embodiments, the tungsten oxide is crystalline,nanocrystalline, or amorphous. In some embodiments, the tungsten oxideis substantially nanocrystalline, with grain sizes, on average, fromabout 5 nm to 50 nm (or from about 5 nm to 20 nm), as characterized bytransmission electron microscopy (TEM). The tungsten oxide morphology ormicrostructure may also be characterized as nanocrystalline using x-raydiffraction (XRD) and/or electron diffraction, such as selected areaelectron diffraction (SAED). For example, nanocrystalline electrochromictungsten oxide may be characterized by the following XRD features: acrystal size of about 10 to 100 nm, for example, about 55 nm. Further,nanocrystalline tungsten oxide may exhibit limited long range order, forexample, on the order of several (about 5 to 20) tungsten oxide unitcells.

The remainder of process flow 200, in FIG. 2, including the formation ofEC layer 306, will be further described in relation to an embodiment,represented in FIG. 3. As mentioned with reference to FIG. 2, an EClayer is deposited, see 205. In embodiments such as the illustratedembodiment of FIG. 3, a substantially homogeneous EC layer, 306,including WO₃ is formed as part of stack 320, where the EC layer 306 isin direct contact with a CE layer 310. In one embodiment, the EC layer306 includes WO₃ as described above. In one embodiment, heating isapplied during deposition of at least a portion of the WO₃. In oneembodiment, several passes are made past a sputter target, where aportion of the WO₃ is deposited on each pass, and heating is applied,for example to substrate 302, after each deposition pass to conditionthe WO₃ prior to deposition of the next portion of WO₃ of EC layer 306.In other embodiments, the WO₃ layer may be heated continually duringdeposition, and deposition can be done in a continuous manner, ratherthan several passes with a sputter target. In one embodiment, the EClayer 306 is about 300 nm to about 600 nm thick. As mentioned, thethickness of the EC layer 306 depends on upon the desired outcome andmethod of forming the interfacial region 180, which serves as an IClayer.

In embodiments described in relation to FIG. 3, the EC layer includesWO₃, about 500 nm to about 600 nm thick, that is sputtered using atungsten target and a sputter gas including about 40% to about 80% O₂and about 20% Ar to about 60% Ar, and where the substrate upon which theWO₃ is deposited is heated, at least intermittently, to about 150° C. toabout 450° C. during formation of the EC layer. In a particularembodiment, the EC layer includes WO₃, about 550 nm thick, sputteredusing the tungsten target, where the sputter gas includes about 50% toabout 60% O₂ and about 40% to about 50% Ar, and the substrate upon whichthe WO₃ is deposited is heated, at least intermittently, to about 250°C. to about 350° C. during formation of the electrochromic layer. Inthese embodiments, the WO₃ of the EC layer is substantially homogenous.In one embodiment, the WO₃ of the EC layer is substantiallypolycrystalline. It is believed that heating the WO₃, at leastintermittently, during deposition aids in formation of a polycrystallineform of the WO₃. It is important that the surface roughness of thetransparent conducting layer (e.g., TEC layer) is reduced, particularlywhen a crystalline layer, such as crystalline WO₃, is to be used atopthe transparent conducting layer.

As mentioned herein, a number of materials are suitable for the EC layer(e.g., layer 306) of embodiments. Generally, in electrochromicmaterials, the colorization (or change in any optical property—forexample, absorbance, reflectance, and transmittance) of theelectrochromic material is caused by reversible ion insertion into thematerial (for example, intercalation) and a corresponding injection of acharge balancing electron. Typically, some fraction of the ionresponsible for the optical transition is irreversibly bound up in theelectrochromic material. As described herein, some or all of theirreversibly bound ions are used to compensate “blind charge” in thematerial. In most electrochromic materials, suitable ions includelithium ions (Li⁺) and hydrogen ions (H⁺) (i.e., protons). In somecases, however, other ions will be suitable. These include, for example,deuterium ions (D⁺), sodium ions (Na⁺), potassium ions (K⁺), calciumions (Ca⁺⁺), barium ions (Ba⁺⁺), strontium ions (Sr⁺⁺), and magnesiumions (Mg⁺⁺). In various embodiments described herein, lithium ions areused to produce the electrochromic phenomena. Intercalation of lithiumions into tungsten oxide (WO_(3−y) (0<y≤˜0.3)) causes the tungsten oxideto change from transparent (bleached state) to blue (colored state). Ina typical process where the EC layer includes or is tungsten oxide,lithium is deposited, for example via sputtering, on the EC layer (e.g.,layer 306) to satisfy the blind charge, see 225 of the process flow inFIG. 2. In one embodiment, the lithiation is performed in an integrateddeposition system where vacuum is not broken between deposition steps.It should be noted that in some embodiments, lithium is not added atthis stage, but rather can be added after deposition of the counterelectrode layer or in other embodiments lithium is added after thesecond TCO (e.g., 312 in FIG. 3) is deposited. In the context of thedescribed embodiments, successful intercalation of lithium into thedevice layers may depend on the morphology of the layers, which in turncan be adversely affected by too high surface roughness of thetransparent conductor upon which they are fabricated.

In embodiments, lithiation can be performed at or between one or moresteps in the process of depositing the EC device on polished transparentconducting layer 304 as described at step 115 of FIG. 1. For example,lithium can be added after deposition of the electrochromic layer, afterdeposition of the counter electrode layer (e.g., 310), or both. Asanother example, lithium can be added after the second TCO 312 isdeposited. In the illustrated example of FIG. 2, lithium is added atstep 215 after the deposition of the electrochromic layer at step 210,lithium is added at step 220 after the deposition of the counterelectrode layer at step 215, and excess lithium is added at step 225after step 220.

Referring again to FIG. 3, a counter electrode layer, 310, is depositedon an electrochromic layer 306. In some embodiments, the counterelectrode layer 310 is inorganic and/or solid. The counter electrodelayer 310 may include one or more of a number of different materialsthat are capable of serving as reservoirs of ions when theelectrochromic device is in the bleached state. During an electrochromictransition initiated by, for example, application of an appropriateelectric potential, the counter electrode layer 310 transfers some orall of the ions it holds to the electrochromic layer 306, changing theelectrochromic layer 306 to the colored state. Concurrently, in the caseof NiO and/or NiWO, the counter electrode layer 310 colors with the lossof ions.

In some embodiments, suitable materials for the counter electrode layer310 include nickel oxide (NiO), nickel tungsten oxide (NiWO), nickelvanadium oxide, nickel chromium oxide, nickel aluminum oxide, nickelmanganese oxide, nickel magnesium oxide, chromium oxide (Cr₂O₃),manganese oxide (MnO₂), and Prussian blue. Optically passive counterelectrodes include cerium titanium oxide (CeO₂—TiO₂), cerium zirconiumoxide (CeO₂—ZrO₂), nickel oxide (NiO), nickel-tungsten oxide (NiWO),vanadium oxide (V₂O₅), and mixtures of oxides (for example, a mixture ofNi₂O₃ and WO₃). Doped formulations of these oxides may also be used,with dopants including, for example, tantalum and tungsten. Because thecounter electrode layer 310 contains the ions used to produce theelectrochromic phenomenon in the electrochromic material when theelectrochromic material is in the bleached state, the counter electrodelayer 310 may have a high transmittance and a neutral color when itholds significant quantities of these ions. The counter electrode layer310 morphology may be crystalline, nanocrystalline, or amorphous.

In some embodiments, where the counter electrode layer 310 isnickel-tungsten oxide, the counter electrode material is amorphous orsubstantially amorphous. Substantially amorphous nickel-tungsten oxidecounter electrodes have been found to perform better, under someconditions, in comparison to their crystalline counterparts. Theamorphous state of the nickel-tungsten oxide may be obtained through theuse of certain processing conditions, described below. Amorphousnickel-tungsten oxide may be produced by relatively higher energy atomsin the sputtering process. Higher energy atoms are obtained, forexample, in a sputtering process with higher target powers, lowerchamber pressures (i.e., higher vacuum), and smaller source to substratedistances. Under the described process conditions, higher density films,with better stability under UV/heat exposure are produced.

In certain embodiments, the amount of nickel present in thenickel-tungsten oxide can be up to about 90% by weight of the nickeltungsten oxide. In a specific embodiment, the mass ratio of nickel totungsten in the nickel tungsten oxide is about 4:6 to 6:4, in oneexample, about 1:1. In one embodiment, the NiWO is about 15% (atomic) Nito about 60% Ni, and about 10% W to about 40% W. In another embodiment,the NiWO is about 30% (atomic) Ni to about 45% Ni, and about 15% W toabout 35% W. In yet another embodiment, the NiWO is about 30% (atomic)Ni to about 45% Ni, and about 20% W to about 30% W. In yet anotherembodiment, the NiWO is about 42% (atomic) Ni and about 14% W.

In embodiments such as the illustrated embodiment of FIG. 2, the CElayer 310 includes NiWo and is a NiWO CE layer as described above. Inone embodiment, the CE layer 310 is about 150 nm to about 300 nm thick,in another embodiment about 200 nm to about 250 nm thick, in anotherembodiment about 230 nm thick.

In a typical process of an embodiment, lithium is also applied to the CElayer until the CE layer is bleached. It should be understood thatreference to a transition between a colored state and bleached state isnon-limiting and suggests only one example, among many, of anelectrochromic transition that may be implemented. Unless otherwisespecified herein, whenever reference is made to a bleached-coloredtransition, the corresponding device or process encompasses otheroptical state transitions such non-reflective-reflective,transparent-opaque, etc. Further, the term “bleached” refers to anoptically neutral state, for example, uncolored, transparent, ortranslucent. Still further, unless specified otherwise herein, the“color” of an electrochromic transition is not limited to any particularwavelength or range of wavelengths. As understood by those of skill inthe art, the choice of appropriate electrochromic and counter electrodematerials governs the relevant optical transition.

In a particular embodiment, lithium, for example via sputtering, isadded to a NiWO CE layer, see 220 of FIG. 2. In a particular embodiment,an additional amount of lithium is added after sufficient lithium hasbeen introduced to fully bleach the NiWO, see 225 of FIG. 2 (thisprocess step 225 is optional, and in one embodiment excess lithium isnot added at this stage in the process). In one embodiment, thisadditional amount is about 5% to about 15% excess lithium based on thequantity required to bleach the counter electrode layer. In anotherembodiment, the excess lithium added to the CE layer is about 10% excessbased on the quantity required to bleach the counter electrode layer.After CE layer 310 is deposited, bleached with lithium and additionallithium is added, a second TCO layer, 312, is deposited on top of thecounter electrode layer, see 230 of FIG. 2. In one embodiment, thesecond TCO layer 312 includes indium tin oxide, in another embodiment,the second TCO layer is indium tin oxide. In one embodiment, this secondTCO layer 312 is about 20 nm to about 1200 nm thick, in anotherembodiment about 100 nm to about 600 nm thick, and in another embodimentabout 350 nm thick.

Referring again to FIG. 3, once layered structure 300 is complete, it issubjected to thermochemical conditioning which converts at least aportion of stack 320 to a region functioning as an IC layer (if it wasnot already converted due to lithium diffusion or other mechanism). Inparticular, an interfacial region, 318, serving as an ion conducting butelectrically insulating layer, is formed between layers 310 and 306after or during deposition of layers 306 and 310. This interfacialregion 318 may span a very thin space between the EC and CE layers; thatis, it is believed to be a diffuse but relatively localized regionbetween the electrochromic and counter electrode layers. Thus it is nota layer itself in the conventional sense. Surface roughness of the first(polished) transparent conducting layer 304 upon which theelectrochromic device is fabricated may disrupt this interfacial region318 and thereby dramatically adversely affect the function of theinterfacial region 318. Methods described herein avoid this result.

Referring again to FIG. 2, layered structure 300 is subjected to amultistep thermochemical conditioning (MTCC), see 235. In oneembodiment, the stack is first subjected to heating, under inertatmosphere (e.g., argon) at about 150° C. to about 450° C., for about 10minutes to about 30 minutes, and then for about 1 minute to about 15minutes under O₂. In another embodiment, the stack is heated at about250° C. for about 15 minutes under inert atmosphere, and then about 5minutes under O₂. Next, layered structure 300 is subjected to heating inair. In one embodiment, the stack is heated in air at about 250° C. toabout 350° C., for about 20 minutes to about 40 minutes; in anotherembodiment, the stack is heated in air at about 300° C. for about 30minutes. The energy required to implement MTCC need not be radiant heatenergy. For example, in one embodiment ultraviolet radiation is used toimplement MTCC. Other sources of energy could also be used.

After the MTCC at 235, process flow 200 is complete and a functionalelectrochromic device is created. It is believed that the lithium instack 320 along with a portion of EC layer 306 and/or CE layer 310 maycombine to form interfacial region 318 which functions as an IC layer.Interfacial region 318 is believed to be primarily lithium tungstate,Li₂WO₄, which is known to have good ion conducting andelectronically-insulating properties relative to traditional IC layermaterials. As discussed above, precisely how this phenomenon occurs isnot yet known. There are chemical reactions that must take place duringthe MTCC to form the ion conducting electronically-insulating region 318between the EC and CE layers, but also it is thought that an initialflux of lithium traveling through the stack, for example provided by theexcess lithium added to the CE layer as described above, plays a part information of interfacial region 318. The thickness of the ion conductingelectronically-insulating region may vary depending on the materialsemployed and process conditions for forming the region. In someembodiments, interfacial region 318 is about 10 nm to about 150 nmthick, in another embodiment about 20 nm to about 100 nm thick, and inother embodiments about 30 nm to about 50 nm thick. Thickness in thisrespect does not refer to a defined layer, as region 318 seems to be agraded composition that varies in density; however it lies between EClayer 306 and CE layer 310.

As mentioned above, there are a number of suitable materials for makingthe EC layer 308. As such, using, for example lithium or other suitableions, in the methods described above one can make other interfacialregions that function as IC layers starting from oxygen rich ECmaterials. Suitable EC materials for this purpose include, but are notlimited to SiO₂, Nb₂O₅, Ta₂O₅, TiO₂, ZrO₂ and CeO₂. In particularembodiments where lithium ions are used, ion conducting materials suchas but not limited to, lithium silicate, lithium aluminum silicate,lithium aluminum borate, lithium aluminum fluoride, lithium borate,lithium nitride, lithium zirconium silicate, lithium niobate, lithiumborosilicate, lithium phosphosilicate, and other such lithium-basedceramic materials, silicas, or silicon oxides, including lithiumsilicon-oxide can be made as interfacial regions that function as IClayers.

In one embodiment, the precursor of the ion conducting interfacialregion is an oxygen-rich (super-stoichiometric) layer that istransformed into an ion-conducting/electron-insulating region vialithiation and MTCC as described herein. It is believed that uponlithiation, the excess oxygen may form lithium oxide, which furtherforms lithium salts, that is, lithium electrolytes, such as lithiumtungstate (Li₂WO₄), lithium molybdate (Li₂MoO₄), lithium niobate(LiNbO₃), lithium tantalate (LiTaO₃), lithium titanate (Li₂TiO₃),lithium zirconate (Li₂ZrO₃) and the like. In one embodiment, theinterfacial region comprises at least one of tungsten oxide (WO_(3+x),0≤x≤1.5), molybdenum oxide (MoO_(3+x), 0≤x≤1.5), niobium oxide(Nb₂O_(5+x), 0≤x≤2), titanium oxide (TiO_(2+x), 0≤x≤1.5), tantalum oxide(Ta₂O_(5+x), 0≤x≤2), zirconium oxide (ZrO_(2+x), 0≤x≤1.5), and ceriumoxide (CeO_(2+x), 0≤x≤1.5).

Any material, however, may be used for the ion conducting interfacialregion 318 provided it can be fabricated with low defectivity and itallows for the passage of ions between the counter electrode layer 310to the electrochromic layer 306 while substantially preventing thepassage of electrons. The material may be characterized as beingsubstantially conductive to ions and substantially resistive toelectrons. In one embodiment, the ion conductor material has an ionicconductivity of about 10⁻¹⁰ Siemens/cm (or ohm⁻¹ cm⁻¹) to about 10⁻³Siemens/cm and an electronic resistivity of greater than about 10⁵ohms-cm. In another embodiment, the ion conductor material has an ionicconductivity of about 10⁻⁸ Siemens/cm to about 10⁻³ Siemens/cm and anelectronic resistivity of greater than about 10¹⁰ ohms-cm. While ionconducting layers should generally resist leakage current (for example,providing a leakage current of not more than about 15 μA/cm² or not morethan about 10 μA/cm², or not more than about 5 μA/cm². It has been foundthat some electrochromic devices fabricated as described herein havesurprising high leakage currents, for example, about 40 μA/cm to about150 μA/cm, yet provide good color change across the device and operateefficiently. There is the possibility that formation of the interfacialregion may be self-limiting and may depend on relative amounts ofoxygen, lithium, electrochromic material and/or counter electrodematerial in the stack.

In accord with the forgoing, one embodiment is a method of fabricatingan electrochromic device, the method including: a) receiving a glasssubstrate having a first transparent conductive coating thereon; b)polishing the first transparent conductive coating using an aluminaslurry having an average particle size of between about 0.1 μM and about1 μM; and c) depositing on the polished transparent conductive coatingthe electrochromic device, the electrochromic device comprising atungsten oxide electrochromic layer, a nickel tungsten oxide counterelectrode layer and a second transparent conducting layer, wherein theelectrochromic device is fabricated in an apparatus where the layers aredeposited without leaving the apparatus and without breaking vacuum. Inone embodiment, the glass substrate is tempered glass and the firsttransparent conductive coating is a tin oxide based material. In anotherembodiment, the glass substrate is non-tempered float glass and thefirst transparent conductive coating is a tin oxide based material. Inone embodiment, the alumina slurry has an average particle size ofbetween about 0.25 μM and about 1 μM. In certain embodiments, c) furtherincludes deposition of lithium metal. In one embodiment, theelectrochromic device is all solid state and inorganic. In oneembodiment, the electrochromic device is as described herein.

EXAMPLE

A sample of float glass coated with a sodium diffusion barrier layer anda fluorinated tin oxide conductive layer thereon (TEC 15 Glass™ byPilkington of Toledo, Ohio) was cut to 26×30 inches and tempered in atempering furnace. The glass light was polished on the transparentconducting coating side using a hand-held rotary polishing tool (Makita9225C) having a polishing pad made of felt and using a pre-mixed slurrypolishing solution (1 μm alumina (Al₂O₃) particles in a water basedslurry with dispersants) obtained from Pace Technologies of Tucson Ariz.The felt pad was kept wet with the alumina slurry during polishing.

The polishing time was determined by measuring the sheet resistance (Rs)value and polishing until the Rs remained at an acceptable level. Thesheet resistance increases with increased polishing time because thethickness of the transparent conducting layer diminishes with increasedpolishing. For example, TEC 15 glass starts with a Rs of ˜13 Ohms/Sq,and was polished until the Rs was 25 Ohms/Sq. The Rs was measured usinga hand-held 4-pt probe device. For a 26×30 inch transparent substrate,the polishing to reach the Rs value above was about 90 minutes.

Studies on smaller area transparent substrates show that the Ra wasimproved by more than 2.5 times. The table below shows the Ra, Rq, andRmax values before and after polishing. Similar results were obtainedusing ceria (cerium oxide, CeO₂) as the abrasive agent. Ra and Rq areprofile surface roughness parameters. Ra is the average roughness and Rqis the root mean squared roughness.

After polishing, the glass surface is cleaned with a polish (cleaning)solution from GlassRenu of Pacheco, Calif. Then the glass is hand-washedin a tub of water to remove additional polishing powder from the glassedges. Next, the glass is washed in an automatic cleaner such as acommercial tool made by Lisec™ (a trade name for a glass washingapparatus and process available from Maschinenbau Gmbh of Seitenstetten,Austria). The haze of the glass was measured by a spectrophotometerprior to polishing to be 1.3%, and after polishing and cleaning the hazewas 0.8%. After cleaning, the glass is then ready for fabrication of anelectrochromic device thereon, e.g., as described herein.

Rmax Ra (nm) Rq (nm) (nm, 5 μm x 5 μm) Unpolished TEC 6.9 8.6 66.3Alumina Polished 2.7 3.5 31 TEC (10 min)FIG. 4 shows TEMs of a transparent conductor layer, in this example aTEC layer, polished and non-polished, left and right TEM, respectively.A white dotted line is superimposed on the TEM of non-polished TEC toshow the topology. The polished TEC layer shows a very smooth surface.In this example, the non-polished TEC layer started with a thickness ofabout 365 nm, and after polishing was about 355 nm thick. An EC devicewas fabricated on each of the respective TEC covered substrates. Thewhite layer below each TEC layer is a sodium diffusion barrier (denoted“DB”) used on the glass substrates (not shown). Electrochromic devicesfabricated on substrates processed in the described manner not onlydisplay very low haze, but also improved functionality.

A recitation of “transparent conductive layer” or “transparentconductor” is intended to mean “transparent conducting layer” unlessspecifically indicated to the contrary.

The above description is illustrative and is not restrictive. Manyvariations of the disclosure will become apparent to those skilled inthe art upon review of the disclosure. The scope of the disclosureshould, therefore, be determined not with reference to the abovedescription, but instead should be determined with reference to thepending claims along with their full scope or equivalents.

One or more features from any embodiment may be combined with one ormore features of any other embodiment without departing from the scopeof the disclosure. Further, modifications, additions, or omissions maybe made to any embodiment without departing from the scope of thedisclosure. The components of any embodiment may be integrated orseparated according to particular needs without departing from the scopeof the disclosure.

What is claimed is:
 1. A method comprising: fabricating anelectrochromic window by: a) polishing a surface of a first transparentconducting layer disposed on a glass substrate; and then b) fabricatingan all solid state and inorganic electrochromic device on the firsttransparent conducting layer, wherein: the electrochromic devicecomprises an electrochromic layer, a counter electrode layer and asecond transparent conducting oxide layer; and the glass substrate istempered prior to a).
 2. The method of claim 1, wherein polishingreduces haze of the first transparent conducting layer to less than 1%.3. The method of claim 1, wherein the transparent conducting layer is atin oxide based material.
 4. The method of claim 3, wherein the tinoxide based material comprises fluorinated tin oxide.
 5. The method ofclaim 1, wherein a) includes an abrasive preparation comprisingparticles having a Mohs hardness scale factor of at least
 9. 6. Themethod of claim 5, wherein the abrasive preparation comprises one orboth of alumina and carborundum.
 7. The method of claim 5, wherein theabrasive preparation is an alumina slurry having an average particlediameter of 250 nm or greater.
 8. The method of claim 7, wherein theaverage particle diameter is about 1 μM.
 9. The method of claim 1,wherein a) is performed for between about 10 minutes and about 90minutes.
 10. The method of claim 1, wherein a) is performed until thesurface roughness of the transparent conducting layer has an Ra value ofbetween about 1 nm and about 5 nm.
 11. The method of claim 1, wherein a)is performed until sheet resistance of the transparent conducting layeris between 5 and 30 Ohms per square.
 12. The method of claim 1, whereinsheet resistance of the transparent conducting layer is periodicallymeasured during a).
 13. The method of claim 1, wherein: theelectrochromic layer includes tungsten oxide; the counter electrodelayer includes nickel tungsten oxide; and the second transparentconducting layer includes tin-oxide.
 14. The method of claim 1, wherein:the electrochromic layer includes tungsten oxide or doped tungstenoxide; the counter electrode layer includes nickel oxide or nickeltungsten oxide, each optionally doped; and fabricating theelectrochromic device includes: depositing the electrochromic layer inone or more portions on the polished surface; depositing the counterelectrode layer on the electrochromic layer to form a device stack,wherein one or both of the electrochromic layer and the counterelectrode layer includes a layer region comprising a greater thanstoichiometric amount of oxygen, the layer region being located at theinterface of the electrochromic layer and the counter electrode layer;and heating the device stack to convert the layer region to an ionconducting and electrically insulating region between the electrochromicand counter electrode layers.
 15. The method of claim 14, furthercomprising applying lithium to the counter electrode layer prior toheating the device stack.
 16. The method of claim 14, wherein heatingthe device stack includes: heating the device stack in an inertatmosphere, then, heating the device stack in O₂, and, subsequently,heating the device stack in air.
 17. The method of claim 14, wherein theion conducting and electrically insulating region includes one oflithium tungstate, lithium molybdate, lithium niobate, lithiumtantalate, lithium titanate, and lithium zirconate.
 18. The method ofclaim 17, wherein the ion conducting and electrically insulating regionincludes one of tungsten oxide, molybdenum oxide, niobium oxide,titanium oxide, tantalum oxide, zirconium oxide, and cerium oxide.